Dynon D180 and RPM

cfiidon · #1 09-12-2012, 09:46 AM

For the last few days I have been attempting to set up the fuel system on my XIO-360 with an AE400 fuel injection system. The first thing I noticed was that I could not seem to reduce the idle fuel pressure to 6-8 psi at 750 RPM.

I borrowed a calibrated gauge and it looked like the lowest was 11+ psig.

Also, I figured the whole system was way out of whack because I couldn't get above 1350 RPM or so at full throttle. It sounded like high rpm but maybe not... the canopy was open and I don't have a calibrated ear.

I decided I would check my tach on the D180 and make sure it was reading correctly. I used an optical rpm meter and it looked like the meter was reading twice my D180 indicated RPM. "something must be wrong with the meter"... right ?!?!?

I scratched my noodle for awhile wondering if the D180 resistors on the p leads might need to be larger. Then the light went on.

Pulses per revolution is a parameter in the D180 menus. The Lycoming 4 cyl selection on setup put it to a value of 2 automatically. If I change it to 1, then my D180 tach reads correctly. This explains why I could not get idle fuel pressure down to 6-8... I was not at an idle of 750, but 1500!

I still don't get it though. If the parameter is pulses per revolution on the mag p-lead, wouldn't there be four pulses per revolution on a 4 cylinder? The Dynon D180 manual just says the parameter is normally set to 1/2 or 1/4th the number of cylinders. So that means 1 or 2. Two obviously didn't work, so it must be 1.

Anyone enlighten me out there?

I'm still not done. As I left it yesterday the pressures were good at idle but the idle was not very smooth. Of course I need to adjust mixture at the throttle body again and we'll see if it smooths out. It's definitely an iterative process.

aerhed · #2 09-12-2012, 10:13 AM

Otto cycle.

cfiidon · #3 09-12-2012, 10:43 AM

Duh-er. They don't call it a four stroke for nothing.

flyinga · #4 09-12-2012, 11:08 AM

I had to use the same setting (1) on my FD 180 to get the tach to read correctly. I have an IO 360 with mags. I believe the install manual says you may have to try different numbers to get the tach to read correctly but I've slept since I completed the Dynon setup so I may have dreamt it.

cfiidon · #5 09-12-2012, 05:21 PM

Thanks gents. I am now more enlightened. And so perhaps the next builder that needs a hand...

Don